Convert Current from Amperes to Milliamperes (A to mA)

Ampere to Milliampere Conversion Formula

Example

Let's convert 5 Ampere (A) to Milliampere (mA).

Using the formula:

Therefore, 5 Ampere (A) is equal to 5000 Milliampere (mA).

How many amperes are in one milliampere? One Milliampere (mA) contains 0.001 Amperes (A) — the inverse of the factor above. Multiplying by 1000 takes you from amperes to milliamperes; multiplying by 0.001 brings you back.

Put in words: one ampere equals 1000 milliamperes, so the ampere is the larger unit of this pair. Converting between them never changes the amount of current being measured — only the size of the unit you count it in.

What Is an Ampere (A)?

An Ampere, often shortened to "amp" or A, is the standard base unit used to measure electric current.

It's part of the International System of Units (SI), which is the modern form of the metric system.

What Does an Ampere Measure in Simple Terms?

In practical terms, the Ampere measures the rate of flow of electric charge, or the amount of electrical current.

A common analogy is to compare electricity to water flowing through a pipe. In this scenario, voltage is the water pressure, while the Ampere (or "amp") represents the volume of water flowing past a certain point per second.

A higher amperage means more electrons are flowing.

This is why high-power devices like space heaters, hair dryers, or power tools require a much higher amp rating (e.g., 10-15 amps). In contrast, small devices like LED lights or phone chargers use much less (often 1-2 amps).

The Official Definition of an Ampere

While the practical definition is most straightforward, the official scientific definition was updated in 2019.

Today, the Ampere is defined based on the elementary charge (e), which is the electric charge of a single proton. This value is fixed at exactly 1.602176634 × 10^-19 Coulombs.

This modern definition ties the Ampere directly to a fundamental constant of nature, ensuring its stability and precision.

An Ampere represents the flow of one Coulomb of charge (approximately 6.242 x 10¹⁸ elementary charges) passing a point in one second.

Who Is the Ampere Named After?

The Ampere is named in honor of André-Marie Ampère (1775-1836), a renowned French physicist and mathematician.

He is widely considered one of the principal founders of the science of electromagnetism, which he termed "electrodynamics."

His most famous contribution is Ampère's circuital law, which mathematically describes the magnetic force between two electrical currents. Naming the unit of current after him recognizes his foundational work in understanding the relationship between electricity and magnetism.

What is a Milliampere (mA)?

A milliampere (mA) is a crucial unit used to measure small amounts of electrical current.

Think of electrical current like the flow of water through a pipe. If a large pipe represents an ampere (A)—the standard unit for current—then a milliampere would be the tiny trickle of water flowing through a drinking straw.

It is part of the International System of Units (SI) and is equal to one-thousandth of an ampere.

1 A = 1,000 mA.

How is a Milliampere Defined?

The milliampere is a standard submultiple of the ampere, the base unit for electrical current.

The prefix "milli" signifies one-thousandth (10^-3).

This standardized measurement ensures that engineers, scientists, and technicians worldwide are using consistent values for measuring electricity.

What Are Milliamperes Used For?

Because a milliampere represents a very small amount of current, it is the perfect unit for measuring the power consumption of everyday small electronics.

You'll see mA used to describe the electricity needed for:

• LED lights: The tiny indicator lights on your TV or computer modem.
• Sensors: Components inside devices that detect things like light, motion, or temperature.
• Microcontrollers: The mini-computers that run your smart appliances and other devices.
• Smartphone Batteries: You've likely seen your phone battery capacity listed in milliampere-hours (mAh). This critical unit tells you how much electrical current the battery can provide over a specific period. For example, a 5,000 mAh battery can supply 5,000 milliamperes of current for one hour.

Why Milliamperes Decide Electrical Safety

Electrical injury is governed by current through the body, not by voltage — which is why safety literature is written in milliamperes.

The commonly cited thresholds for a 50/60 Hz current passing hand-to-hand through an adult are:

• About 1 mA — the threshold of perception, felt as a faint tingle.
• 5–10 mA — painful shock; muscles begin to react involuntarily.
• 10–20 mA — the let-go threshold. Above it, forearm muscles contract hard enough that the victim cannot release the conductor, which is what turns a brief contact into a sustained one.
• Above roughly 100 mA — current through the chest can trigger ventricular fibrillation, the mechanism behind most electrocution deaths.

The numbers explain a detail that often looks strange: a residual-current device (RCD or GFCI) trips at just 30 mA in Europe or 5 mA in North America. Those settings sit deliberately below the fibrillation range, not below the level at which a shock hurts. The device is not there to prevent a shock — it is there to cut the circuit before that shock becomes fatal.

The 4–20 mA Current Loop

Industrial instrumentation transmits measurements as a current between 4 and 20 mA rather than as a voltage, and the choice is deliberate.

Current is identical at every point in a series loop, so voltage drop along a long cable run — which would corrupt a voltage signal — has no effect on the reading. The live zero at 4 mA is equally purposeful: a healthy sensor reading its minimum still draws 4 mA, so a reading of 0 mA can only mean a broken wire or dead transmitter. A 0–20 mA scheme could not distinguish "minimum value" from "cable cut".

Ampere to Milliampere Conversion Table

Here are some quick reference conversions from Ampere (A) to Milliampere (mA):